DeKalb County expects by January to approve school closings to reduce the number of “empty seats” — as many as 16,000, or more than 500 classrooms — over the next six years. At-risk schools are clustered primarily in southwest, central and east DeKalb. (The math seems a little fuzzy, as individual schools’ numbers do NOT necessarily add up to the totals printed on maps released Friday. No one said you’d have to do math to close schools, right?)